Early-onset Alzheimer's is an uncommon form of dementia that strikes people younger than age 65. Of all the people who have Alzheimer's disease, about 5 percent develop symptoms before age 65. So if 4 million Americans have Alzheimer's, at least 200,000 people have the early-onset form of the disease.

Most people with early-onset Alzheimer's develop symptoms of the disease in their 40s and 50s.

Some people with early-onset Alzheimer's have the most common form of the disease. Experts don't know why these people get the disease at a younger age than others do.

But others with early-onset Alzheimer's have a type of the disease called "familial Alzheimer's disease." They're likely to have a parent or grandparent who also developed Alzheimer's at a younger age.

Early-onset Alzheimer's that runs in families is linked to three genes — the APP, PSEN 1 and PSEN 2 — that differ from the APOE gene that can increase your risk of Alzheimer's in general.

Together, these three genes account for less than 1 percent of all Alzheimer's disease cases but about 60 to 70 percent of early-onset Alzheimer's cases. If you have a genetic mutation in one of those three genes, you may develop Alzheimer's before age 65.

Genetic testing for these mutations is available, but anyone who's considering it should pursue genetic counseling — to examine the pros and cons beforehand.

For example, it may be helpful to consider how a positive test may affect your eligibility for long-term care, disability and life insurance.

On the other hand, if you know you carry a form of the early-onset genes, you may be able to take steps to make it easier for you and your loved ones to cope with the effects of the disease.

If you have early-onset Alzheimer's linked to one of the three genes or carry a form of these genes without symptoms, talk to your doctor about participating in a research study. By studying the early-onset form of Alzheimer's, researchers hope to learn more about the causes and progression of the disease and develop new treatments.

An accurate diagnosis of early-onset Alzheimer's is crucial for medical reasons to rule out other potential issues and get the most appropriate treatment as well as for personal and professional reasons.

For you and your family, the diagnosis is fundamental in helping the family respond with appropriate understanding and compassion. It can also give you and your family more time to make important decisions about financial and legal issues.

At work, it can allow you to explain your condition to your employer and perhaps arrange a lighter workload or more convenient schedule.

Alzheimer's disease has a tremendous impact at any age. But people with early-onset Alzheimer's disease may face some unique challenges.

They may face stigmas and stereotypes about the disease. Due to their young age, people may not believe they have the disease or question the diagnosis.

People with early-onset Alzheimer's may lose relationships or jobs instead as a consequence of this misunderstanding rather than being identified as medically ill or disabled.

They may also face a loss of income from being diagnosed while still working.

Before your condition significantly affects your ability to do your job, talk to your employer. What you can do:

Find out if you can switch to a position that better suits your emerging limitations.

Familiarize yourself and your spouse, partner or caregiver with your benefits, and find out whether an employee assistance program is available.

Explore what benefits may be offered to you under the Americans with Disabilities Act, Family and Medical Leave Act and COBRA.

If you feel overwhelmed, consider reducing your hours or taking time off.

After a diagnosis of early-onset Alzheimer's, spouses or partners often feel a sense of loneliness or loss as they face the possibility of spending many years without an active partner.

Losing the romantic component and changing to a caregiver status also complicates the relationship. Try to:

Talk about what kind of help you need from each other. Communicate about changes you're experiencing and ways in which your needs also may have changed. Don't be afraid to ask for help.

Continue participating in as many activities with your partner that you currently enjoy and adapt as necessary. Or find new activities that you can enjoy together.

Keep a folder of resources you may need as the disease progresses.

Find a counselor who works with couples facing issues you feel challenged by, such as sexuality and changing roles in the relationship.

A diagnosis of early-onset Alzheimer's can also be difficult for children, who may not understand. Children may blame themselves, become angry or react in any number of ways. Try to:

Find activities you can enjoy together.

Stay engaged and talk with your children honestly about what you're experiencing.

Find a support group for children, and invite your kids to some of your counseling sessions. Make your child's school counselor and social worker aware of your condition.

People with early-onset Alzheimer's often have to quit work, and this loss of income is a serious concern. Finances get even tighter if spouses or partners also quit their jobs to become full-time caregivers.

Some medical benefits and many social-support programs won't provide assistance unless the person with Alzheimer's is older than age 65. Younger people may need special waivers to get into such programs. What you can do:

Talk with a financial planner and an attorney to help you plan for your future financial needs.

Ask your employer whether early retirement is an option.

Explore what benefits may be available to you through Social Security, Medicare or Medicaid.

Key elements of Alzheimer's care are education and support. This is especially true given the unique challenges of early-onset Alzheimer's. Getting connected to services such as support groups can help you identify resources, gain a deeper understanding of the disability and learn ways to adapt.

Remember, you're not alone. Many resources are available to assist you, your family and caregivers to cope with this disease. Options for support may vary depending on where you live.

In the early stages of the disease, be sure that you and your spouse or partner do research and establish a plan for managing the progression of your condition. Knowing you have a plan and have identified support and resources will help everyone in the future.

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